Evaluation of Genetic Breeding Values (GBVs) for Yield-Related Traits and Soluble Solid Content (SSC) of Tomato

Production of tomato (Solanum lycopersicum) in Japan is characterized by consumer demand for high fruit quality. However, unusual weather conditions such as high temperature, are making it difficult for Japanese producers to obtain a steady yield of fruit. Therefore, improvements in the yield as well as the quality are important themes in tomato production and breeding. QTLs contributing to yield-related traits (total fresh weight of fruit and so on) and quality-related soluble solid content (SSC) derived from intraspecific crosses generally show small effects on the phenotypes, therefore, MAS strategies for those traits are limited in practical breeding. Here we report genetic breeding values (GBVs) for those traits to apply genomic selection (GS) approaches in Japanese tomato breeding. Recombinant inbred lines (RILs) derived from a cross of two F₁ hybrids of tomato were used as training population. The parents were Japanese F₁ cultivar ‘Momotaro 8’ (Takii & Company, Ltd., Japan), which was characterized by high sugar content, and the other was high-yield Dutch F₁ cultivar ‘Geronimo’ (De Ruiter Seeds, the Netherlands). This cross corresponds to a four-way cross, as four parental lines of the two F₁ cultivars were considered to be founders. We estimated marker effects on the four founder haplotypes for the traits using the marker genotypes and phenotypes of the RILs with a Bayesian multiple QTL method and predicted the GBVs of F₁ lines derived from crosses among RILs. Correlations between GBVs and phenotypes in F₁ lines were investigated for the evaluation the accuracies of this GBV prediction.